No-one has yet pointed out that NESTED branches use more instructions than EXTENDED branches. Branch Starts (BST) and Branch Ends (BND) are instructions stored in processor memory.
More instructions means more memory used, and worse still, a longer execution time (more instructions to process).
In Alarics post #4, the code stored for the first rung (using extended branches) is....
BST XIC B3:0/0 NXB I:0.0/0 BND BST OTE B3:0/1 NXB OTE O:0.0/0 NXB OTE O:0.0/1 NXB OTE O:0.0/2
And for the second rung (using nested branches) is...
BST XIC B3:0/0 NXB I:0.0/0 BND BST OTE B3:0/1 NXB BST OTE O:0.0/0 NXB BST OTE O:0.0/1 NXB BST OTE O:0.0/2 BND BND BND
The "extra" instructions are in red, these waste memory and processor execution time. There are 12 instructions in the first rung, and 18 in the second, that's 50% wastage !!
Also, on the larger machines (that allow more than four levels of nesting), the rung eventually goes wider than the screen view, making the logic hard to follow. Using Extended branches adds nothing to the rung "width".